These facts can hardly, I think, be interpreted in any other manner than by supposing that the spleen and lymphatic glands are intimately concerned in the production of the formed elements of the blood.
By pyæmia is meant pus corpuscles in the blood. But most cases of so-called pyæmia are really cases in which there is an increase of white blood corpuscles, and it is doubtful whether such a condition as pus in the blood does ever occur. In the extremely rare cases, in which pus breaks through into the veins, purulent ingredients may, without doubt, be conveyed into the blood, but in such cases the introduction of pus occurs for the most part but once, and there is no persistent pyæmia. Even when clots in veins break down and form matter like pus, it will be found that the matter is not really pus, and contains no pus cells.
Chlorosis is a condition in which there is a diminution of the cellular elements of the blood, due probably to their deficient formation in the spleen and lymphatic glands.
The Vital Processes and Their Relation to Disease. Inflammation
The study of the histology of the nervous system shows that in all parts of the body a splitting up into a number of small centres takes place, and that nowhere does a single central point susceptible of anatomical demonstration exist from which the operations of the body are directed. We find in the nervous systems definite little cells which serve as centres of motion, but we do not find any single ganglion cell in which alone all movement in the end originates. The most various individual motor apparatuses are connected with the most various individual motor ganglion cells. Sensations are certainly collected in definite ganglion cells. Still, among them, too, we do not find any single ganglion cell which can be in any way designated the centre of all sensation, but we again meet with a great number of very minute centres. All the operations which have their source in the nervous system, and there certainly are a very great number of them, do not allow us to recognise a unity anywhere else than in our own consciousness. An anatomical or physiological unity has at least as yet been nowhere demonstrated.
When we talk of life we mean vital activity. Now, every vital action supposes an excitation or irritation. The irritability of the part is the criterion by which we judge whether it be alive or not. Our notion of the death of a part is based upon nothing more or less than this—that we can no longer detect any irritability in it. If we now proceed with our analysis of what is to be included in the notion of excitability, we at once discover, that the different actions which can be provoked by the influence of any external agency are essentially of three kinds. The result of an excitation or irritation may, according to circumstances, be either a merely functional process, or a more or less increased nutrition of the part, or a formative process giving rise to a greater or less number of new elements. These differences manifest themselves more or less distinctly according as the particular tissues are more or less capable of responding to the one or other kinds of excitation. It certainly cannot be denied that the processes may not be distinctly defined, and that between the nutritive and formative processes, and also between the functional and nutritive ones there are transitional stages; still, when they are typically performed, there is a very marked difference between them, and considerable differences in the internal changes undergone by the excited parts.
In inflammation all three irritative processes occur side by side. Indeed, we may frequently see that when the organ itself is made up of different parts, one part of the tissue undergoes functional or nutritive, another formative, changes. If we consider what happens in a muscle we see that a chemical or traumatic stimulus produces a functional irritation of the primitive fasciculi, with contraction of the muscle followed by nutritive changes. On the other hand, in the interstitial connective tissue which binds the individual fasciculi of the muscle together, real new formations are readily produced, commonly pus. In this manner the three forms of irritation may be distinguished in one part.
The formative process is always preceded by nutritive enlargement due to irritation of the part, and has no connection with irritation of the nerves. Of course there may be also an irritation of the nerves, but this, if we do not take function into account, has no causal connection with the processes going on in the tissue proper, but is merely a collateral effect of the original disturbance.
Besides these active processes of function, nutrition, and new formation, there occur passive processes. Passive processes are called those changes in cells whereby they either lose a portion of their substance, or are so completely destroyed, that a loss of substance, a diminution of the sum total of the constituents of the body is produced. To this class belong fatty degeneration of cells, affection of arteries, calcification, and ossification of arteries, amyloid degeneration, and so forth.
It will now be necessary to consider inflammation at more length. The theory of inflammation has passed through various stages. At first heat was considered as its essential and dominant feature, then redness, then exudative swelling; while the speculative neuropathologists consider pain the fons et origo of the condition.